U.S. patent number 7,734,398 [Application Number 11/495,772] was granted by the patent office on 2010-06-08 for system for automated excavation contour control.
This patent grant is currently assigned to Caterpillar Inc.. Invention is credited to Swaroop Sesha Kamala Manneppalli.
United States Patent |
7,734,398 |
Manneppalli |
June 8, 2010 |
System for automated excavation contour control
Abstract
A control system for a machine is disclosed. The control system
has a ground engaging tool operable to remove material from a
surface at a worksite. The control system also has a controller
configured to generate a desired single-pass excavation contour
prior to engagement of the ground engaging tool with the surface.
The desired single-pass excavation contour has one or more
predefined characteristics.
Inventors: |
Manneppalli; Swaroop Sesha
Kamala (Peoria, IL) |
Assignee: |
Caterpillar Inc. (Peoria,
IL)
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Family
ID: |
38573150 |
Appl.
No.: |
11/495,772 |
Filed: |
July 31, 2006 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20080082238 A1 |
Apr 3, 2008 |
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Current U.S.
Class: |
701/50; 37/414;
37/348; 172/2 |
Current CPC
Class: |
E02F
9/2045 (20130101); E02F 3/842 (20130101) |
Current International
Class: |
G06F
19/00 (20060101) |
Field of
Search: |
;701/50 ;37/348,415,414
;73/146 ;172/2 ;342/357.06,357.17,451 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1 099 802 |
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May 2001 |
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EP |
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2 228 507 |
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Aug 1990 |
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GB |
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57112525 |
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Jul 1982 |
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JP |
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Primary Examiner: To; Tuan C
Attorney, Agent or Firm: Finnegan, Henderson, Farabow,
Garrett & Dunner
Claims
What is claimed is:
1. A control system for a machine, comprising: a ground engaging
tool operable to remove material from a surface at a worksite; and
a controller configured to receive at least one input associated
with a condition of the worksite and to generate a desired
single-pass excavation contour prior to engagement of the ground
engaging tool with the surface, the desired single-pass excavation
contour based on a mathematically derived curve that is modified by
a capacity of the machine and the condition of the worksite; the
controller further configured to control positioning of the ground
engaging tool to follow the single-pass excavation contour.
2. The control system of claim 1, wherein the desired single-pass
excavation contour is a complete trajectory of the tool including
an entry into, movement through, and an exit from the surface.
3. The control system of claim 1, wherein: the controller generates
the desired excavation contour based on a Gaussian curve.
4. The control system of claim 1, wherein the at least one input is
an existing general slope of the surface.
5. The control system of claim 1, wherein the at least one input is
a material condition.
6. The control system of claim 1, wherein the capacity of the
machine is defined by at least one of a maximum drawbar pull force
of the machine.
7. The control system of claim 1, wherein the controller is
configured to modify the curve so that a volume of material
excavated by following the curve is limited to less than a maximum
volume of material movable by the machine.
8. The control system of claim 1, wherein the controller is further
configured to modify the curve based upon an entry into and an exit
from the surface substantially tangent with the surface.
9. The control system of claim 1, wherein the controller is further
configured to modify the curve to includes a slope rate of change
being limited to less than a maximum slope rate of change possible
with the ground engaging tool.
10. The control system of claim 1, wherein the capacity of the
machine is defined by a characteristic of the ground engaging tool,
a maximum drawbar pull force of the machine, or a machine travel
speed.
11. The control system of claim 1, wherein the capacity of the
machine is limited to a percentage of fixed blade load.
12. The control system of claim 11, wherein the percentage of fixed
blade load is less than about 80 percent.
13. A method of controlling a machine's work implement, comprising:
providing a machine capacity input to an electronic controller;
providing a worksite condition input to the electronic controller;
generating a desired machine contour of a work surface based on a
mathematical curve, the mathematical curve being modified by the
machine capacity input and the worksite condition input; and
controlling the position of the work implement to produce the
desired excavation contour.
14. The method of claim 13, wherein the mathematical curve is a
Gaussian curve.
15. The method of claim 13, wherein the mathematical curve has an
entry into and an exit from the work surface substantially tangent
with the work surface.
16. The method of claim 13, wherein: the worksite condition input
is a slope of the work surface; a depth of the desired excavation
contour increases as the slope of the work surface decrease; and a
length of the desired excavation contour decreases as the depth of
the desired excavation contour increases.
17. The method of claim 13, wherein: the worksite condition input
is a material condition of the work surface; and a depth of the
excavation contour increases as the material of the work surface
softens.
Description
TECHNICAL FIELD
The present disclosure relates generally to an automated machine
control system and, more particularly, to a system for
automatically calculating and controlling a machine's excavation
contour.
BACKGROUND
Machines such as, for example, dozers, motor graders, wheel
loaders, and other types of heavy equipment are used to perform a
variety of tasks. Some of these tasks require very precise and
accurate control over operation of the machine that is difficult
for an operator to provide. Other tasks requiring removal of large
amounts of material can be difficult for an unskilled operator to
achieve efficiently. Poor performance and low efficiency can be
costly to a machine owner. Because of these factors, the completion
of some tasks by a completely operator-controlled machine can be
expensive, labor intensive, time consuming, and inefficient.
One method of improving the operation of a machine under such
conditions is described in U.S. Pat. No. 5,005,652 (the '652
patent) issued to Johnson on Apr. 9, 1991. The '652 patent
describes a track laying vehicle carrying a bulldozer blade, which
can be raised or lowered by a pair of hydraulic rams. The rams are
under the control of a control system carried on the vehicle. The
blade carries an upwardly extending mast having a laser beam
detector for receiving signals emitted by a laser-formed reference
plane. In use, the track laying vehicle can be driven forward while
the signal from the laser-formed reference plane is received by the
detector. The detector determines whether a locus of the detector,
the blade, and hence the profile of the work surface being produced
are deviating from a required datum. Upon detection of a deviation,
the control system provides hydraulic control of the rams such that
the detector, blade, and the cut surface are returned to the
correct elevation parallel to the reference plane.
To produce a non-planar surface, a distance wheel may be mounted to
the tracked vehicle of the '652 patent to give a distance
measurement from a starting point. During operation, the blade can
be traversed in a direction generally parallel to the reference
plane while varying the distance of the blade from the reference
plane in accordance with instructions from the control system. The
instructions are issued by the control system in accordance with
the distance measurement transmitted to it by the distance wheel
and a desired contour.
Although the track laying vehicle of the '652 patent may be capable
of producing accurate surface contours during an excavation
process, it may not consider efficiency when doing so. In
particular, the control system associated with the track laying
vehicle does not consider an amount of material being moved during
each excavation pass, a condition of the material, a capacity of
the track laying vehicle to move the material, or a resulting
intermediate contour (e.g., the contour of the surface after a
first excavation pass, but prior to a final excavation pass).
Instead, the control system of the '652 patent is only capable of
blindly following a predefined contour map and, typically, is only
used for final grading operations. For this reason, the track
laying vehicle of the '652 patent may be inefficient at producing
the desired surface contour and at moving large amounts of material
that require multiple excavation passes.
The disclosed system is directed to overcoming one or more of the
problems set forth above.
SUMMARY OF THE INVENTION
In one aspect, the present disclosure is directed to a control
system for a machine. The control system includes a ground engaging
tool operable to remove material from a surface at a worksite. The
control system also includes a controller configured to generate a
desired single-pass excavation contour prior to engagement of the
ground engaging tool with the surface. The desired single-pass
excavation contour has one or more predefined characteristics.
In yet another aspect, the present disclosure is directed to a
method of controlling a machine's work implement. The method
includes generating a desired excavation contour in a work surface
based on a mathematical curve. The method further includes
controlling the position of the work implement to produce the
desired excavation contour.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a pictorial illustration of an exemplary disclosed
machine operating at a worksite;
FIG. 2 is a diagrammatic illustration of an exemplary disclosed
control system for use with the machine of FIG. 1; and
FIG. 3 is a diagrammatic illustration of exemplary excavation
contours generated by the control system of FIG. 2.
DETAILED DESCRIPTION
FIG. 1 illustrates a worksite 10 with an exemplary machine 12
performing a predetermined task. Worksite 10 may include, for
example, a mine site, a landfill, a quarry, a construction site, or
any other type of worksite. The predetermined task may be
associated with altering the current geography at worksite 10 and
may include, for example, a grading operation, a leveling
operation, a bulk material removal operation, or any other type of
geography altering operation at worksite 10.
Machine 12 may embody a mobile machine that performs some type of
operation associated with an industry such as mining, construction,
farming, or any other industry. For example, machine 12 may be an
earth moving machine such as a dozer having a blade or other work
implement 18 movable by way of one or more motors or cylinders 20.
Machine 12 may also include one more traction devices 22, which may
function to steer and/or propel machine 12.
As best illustrated in FIG. 2, machine 12 may include a control
system 16 in communication with components of machine 12 to affect
the operation of machine 12. In particular, control system 16 may
include a power source 24, a means 26 for driving cylinders 20 and
traction device 22, a locating device 28, and a controller 30.
Controller 30 may be in communication with power source 24, driving
means 26, cylinders 20, traction device 22, and locating device 28
via multiple communication links 32, 34, 36a-c, 38, and 40,
respectively.
Power source 24 may embody an internal combustion engine such as,
for example, a diesel engine, a gasoline engine, a gaseous fuel
powered engine, or any other type of engine apparent to one skilled
in the art. Power source 24 may alternatively or additionally
include a non-combustion source of power such as a fuel cell, a
power storage device, an electric motor, or other similar
mechanism. Power source 24 may be connected to drive means 26 via a
direct mechanical coupling, an electric circuit, or in any other
suitable manner.
Driving means 26 may include a pump such as a variable or fixed
displacement hydraulic pump drivably connected to power source 24.
Driving means 26 may produce a stream of pressurized fluid directed
to cylinders 20 and/or to a motor associated with traction device
22 to drive the motion thereof. Alternatively, driving means 26
could embody a generator configured to produce an electrical
current used to drive any one or all of cylinders 20 and traction
device 22, a mechanical transmission device, or any other
appropriate means known in the art.
Locating device 28 may be associated with work implement 18 to
determine a position of work implement 18 relative to machine 12
or, alternatively, to a local reference point or coordinate system
associated with work site 10. For example, locating device 28 may
embody an electronic receiver configured to communicate with one or
more satellites (not shown) or a local radio or laser transmitting
system to determine a relative location of itself. Locating device
28 may receive and analyze high-frequency, low power radio or laser
signals from multiple locations to triangulate a relative 3-D
position. A signal indicative of this position may then be
communicated from locating device 28 to controller 30 via
communication link 40. Alternatively, locating device 28 may embody
an Inertial Reference Unit (IRU), a position sensor associated with
cylinders 20 and/or traction device 22, or any other known locating
device operable to receive or determine positional information
associated with machine 12.
Controller 30 may include means for monitoring, recording, storing,
indexing, processing, and/or communicating the location of machine
12 and for automatically controlling operations of machine 12 in
response to the location. These means may include, for example, a
memory, one or more data storage devices, a central processing
unit, or any other components that may be used to run the disclosed
application. Furthermore, although aspects of the present
disclosure may be described generally as being stored in memory,
one skilled in the art will appreciate that these aspects can be
stored on or read from different types of computer program products
or computer-readable media such as computer chips and secondary
storage devices, including hard disks, floppy disks, optical media,
CD-ROM, or other forms of RAM or ROM.
Controller 30 may be configured to generate a desired excavation
contour based on a mathematical curve, one or more inputs
associated with characteristics of worksite 10, and a capacity of
machine 12. For example, controller 30 may use a Gaussian curve
represented by Eq. 1 below to calculate a desired trajectory of
work implement 18 during a single excavation pass.
.times..times.e.mu..sigma..times. ##EQU00001## wherein: y is a
vertical depth of cut below the work surface; A is a variable that
limits the maximum depth of cut; x is the horizontal travel
distance along the work surface; .mu. is a variable associated with
a horizontal location of the maximum dept of cut; .sigma. is a
variable associated with a rate of change of the excavation contour
slope; and n is another variable that can affect the rate of change
of the excavation contour slope.
When generating the Gaussian curve from Eq. 1 above, controller 30
may select the variables .mu., .sigma., and n based on a condition
of worksite 10. In particular, one or more maps relating an
operating slope of machine 12, a material composition of worksite
10, a viscosity of worksite 10, or other such worksite-associated
condition to the variables .mu., .sigma., and n may be stored in
the memory of controller 30. Each of these maps may include a
collection of data in the form of tables, graphs, and/or equations.
In one example, the material condition of a worksite surface and
the variable .mu. may form the coordinate axis of a 2-D table for
control of the horizontal location of the maximum depth of cut. In
another example, the existing general slope of the surface and the
variable .sigma. may form the coordinate axis of another 2-D table
for control of the entry and/or exit slopes of the excavation
contour. Although in most situations n may be an even number, such
as 2, n may alternatively be related to slope and/or the material
condition (i.e., hardness) of the surface in yet another 2-D table
to affect the entry and/or exit slopes of the excavation contour.
It is contemplated that a set of .mu.-relationship tables, a set of
.sigma.-relationship tables, and/or a set of n relationship tables
may be stored in the memory of controller 30. In this situation,
each table within each set may correspond to a machine condition
such as, for example, a speed of machine 12, an available power
output of machine 12, an attached work implement type, or other
similar machine condition. Controller 30 may allow the operator to
directly modify these maps and/or to select specific maps from
available relationship maps stored in the memory of controller 30
to affect the variables .mu., .sigma., and n based on observed
conditions at worksite 10 or specific modes of machine operation.
It is contemplated that the maps may alternatively be automatically
selected for use and/or modified by controller 30 based on measured
parameters such as, for example, slip, drawbar pull, stall, travel
speed, or other similar parameters indicative of conditions at
worksite 10.
Once the variables .mu., .sigma., and n have been selected for use
in determining the desired excavation contour based on material
and/or machine conditions specific to the current worksite, the
variable A may be determined based on a capacity of machine 12. In
particular, machine 12 may have a maximum capacity to move material
that is fixed according to a size of work implement 18, a maximum
drawbar pull force of machine 12, a travel speed of machine 12, or
other such machine-related limitation. Controller 30 may compare
the desired excavation contour to the capacity of machine 12 and
modify the value of the variable A based on the capacity such that
a maximum volume of material is removed during each excavation
pass, without exceeding the machine's capacity to efficiently move
material along the work surface. In one example, the maximum volume
of material removed during each excavation pass may be limited to
less than about 80% of a fixed blade load. This condition may be
represented by the following equation:
.times..intg..times..times.e.mu..sigma..ltoreq..times..times..times..time-
s..times..times..times..times..times..times..times..times..times..times..t-
imes..times..times..times..times..times..times..times..intg..times..times.-
e.mu..sigma..times..times..times..times..times..times..times..times..times-
..times..times..times..times..times..times..times..times..times..times..ti-
mes..times..times..times..times..times..times..times..times..times..times.-
.times..times..times..times..times..times..times..times..times..times..tim-
es..times..times..times..times..times..times..times..times.
##EQU00002##
When generating the desired excavation contour, other limitations
on the variables of Eq. 1 may also be implemented based on a
capacity of machine 12. For example, the value of the variable
.sigma. may be limited to a minimum threshold value corresponding
to a maximum slope rate of change possible with machine 12. In this
manner, only contours that are possible for machine 12 to follow
may be generated.
When implementing Eq. 1 from above, the generated excavation
contour may also be constrained to positively affect future
excavation passes. In particular, optimal entry and exit slopes of
the excavation contour may be substantially tangential to the work
surface such that abrupt changes in the terrain, which can slow
production of machine 12, are minimized. The nature of the Gaussian
curve may provide these tangential entry and exits slopes. Curves
other than Gaussian-type curves may also provide for this
requirement. These other mathematical curves may include, among
others, trigonometric curves such as a sin or a tangent curve, a
clothoid loop, or segments of a spiral.
Controller 30 may control cylinders 20 and/or traction devices 22
to automatically alter the geography of worksite 10. In particular,
controller 30 may automatically control operations of machine 12 to
engage work implement 18 with the terrain of worksite 10 at the
calculated excavation entry location and slope, move work implement
18 along the trajectory of the determined Gaussian curve, and
remove work implement 18 from the work surface at the appropriate
exit location and slope. Controller 30 may be in communication with
the actuation components of cylinders 20 and/or traction device 22
to raise, lower, and/or orient machine 12 and work implement 18
such that work implement 18 produces the desired excavation
contour. For example, controller 30 may communicate with power
source 24, driving means 26, with various hydraulic control valves
associated with cylinders 20, with transmission devices (not
shown), and/or other actuation components of machine 12 to
initiate, modify, or halt operations of cylinders 20 and traction
device 22, as necessary or desired. It is contemplated that
controller 30 may use locating device 28 and/or other such guidance
and implement positioning systems to accurately control the
operation of machine 12 such that work implement 18 follows the
calculated trajectory of the Gaussian curve. In this manner,
controller 30 may provide for partial or full automatic control of
machine 12. It is contemplated that controller 30 may only
determine the desired excavation contour, then relinquishing
control of machine 12 to an operator, if desired. It is also
contemplated that controller 20 may be located remotely from
machine 12, and only transmit the desired contour to machine
12.
FIG. 3 provides example Gaussian curves calculated for different
worksite conditions. FIG. 3 will be discussed in more detail in the
follow section to further illustrate the disclosed control system
and its operation.
INDUSTRIAL APPLICABILITY
The disclosed control system may be applicable to machines
performing material moving operations where efficiency is
important. In particular, the disclosed control system may, based
on a mathematical curve and one or more machine/worksite related
conditions, determine a desired excavation contour that results in
the efficient removal of earthen material. The disclosed control
system may then automatically control a work implement of the
machine and the machine itself to closely follow the excavation
contour such that efficient removal of the material is achieved.
The operation of control system 16 will now be described.
FIG. 3 illustrates two exemplary excavation contours 42 and 44,
which were determined based on Gaussian curves according to Eq. 1.
In the first example, contour 42 may be associated with machine 10
operating on flat terrain (represented by the horizontal line at
y=0) of hard material. Because of the hardness of the material and
a known capacity of machine 10, .sigma. on entry was set to 4 m
resulting in a gentle entry slope, .sigma. on exit was set to 8 m
resulting in an even more gentle exit slope to accommodate a loaded
work implement 18, .mu. was set for a maximum depth at 5 m from the
start of the excavation contour, n was set to the standard value of
2, and A was thereafter determined to be a fairly shallow depth of
12 cm based on the limited capacity of machine 12 in the hard
terrain. As indicated above, the amount of material that will be
excavated during the pass along contour 42 may be less than about
80% of the maximum blade load of machine 10.
In the example illustrated by contour 44, machine 10 is operating
on downhill terrain (rotated to align with the horizontal line at
y=0 for comparison purposes) of soft material. Because of the slope
and the softness of the material, machine 10 may be capable of more
aggressive excavation (e.g., a more aggressive cut to a deeper
depth resulting in faster loading of machine 10). For this reason,
.sigma. on entry was set to 1.5 m resulting in a steep forceful
entry slope, .sigma. on exit was set to 4 m resulting in a more
gentle slope to accommodate a loaded work implement 18, .mu. was
set for a maximum depth at 2 m from the start of the excavation
contour for quick loading of the soft material by work implement
18, n remained at the standard value of 2, and A was thereafter set
to a depth of 25 cm corresponding to the limited capacity of
machine 10 in the soft surface material. Similar to excavation
contour 42, the amount of material that will be excavated during
the pass along contour 42 may be kept to less than about 80% of the
maximum blade load of machine 10.
From the two examples described above, some general trends may be
observed. In particular, the depth of the desired excavation
contour may increase as the general slope of the work surface
decreases. That is, as the slope of the terrain decreases from
uphill to flat or from flat to downhill, gravity may act on machine
10 to increase its capacity to move material. This increased
capacity may be utilized by increasing the depth of the excavation
contour. Similarly, a depth of the desired excavation contour may
increase as the material of the work surface softens, because the
capacity of the machine to break into and move the material may
increase. As the depth of the desired excavation contour increases,
a length of the desired excavation contour may decrease in order to
remain within the capacity limitations of machine 10. That is, as
the depth of an excavation contour increases, the length may
decrease to keep the amount of removed material to less than the
80% mark. Similar trends may also be observed according to machine
speed prior to excavation entry, wherein a higher initial speed
results in a greater capacity to break into and move material.
Because controller 30 may consider machine capacity and worksite
conditions when determining excavation contours, it may be
efficient at removing large amounts of material from worksite 10.
In particular, because the excavation contours may be based on
machine capacity such as speed, drawbar pull, and size and based on
worksite conditions such as slope and material softness, the
excavation contours may correspond with a maximum amount of
material removable by machine 12 during a single excavation pass.
By ensuring that machine 12 is not unnecessarily over or under
loaded, machine 12 may be operated at peak efficiency. In addition,
because controller 30 may consider the predicted efficiency of
machine 12 through subsequent excavation passes, each pass of
machine 12 may be optimally efficient.
It will be apparent to those skilled in the art that various
modifications and variations can be made to the disclosed control
system. Other embodiments will be apparent to those skilled in the
art from consideration of the specification and practice of the
disclosed control system. It is intended that the specification and
examples be considered as exemplary only, with a true scope being
indicated by the following claims and their equivalents.
* * * * *